Boring bar



F. WALTHER Feb. 15, 1938.

BORING BAR Filed July 3l, 1935 Patented Feb. l5, 1933 UNITED STAT ATETGFFEQE Application July 31, 1935, Serial No. 34,086 In Germany August11, 1934 fi Claims.

This invention relates to a boring bar.

In known boring bars disposed between centers and intended for fine workthe portion carrying the tool can be moved by its own weight at acertain position of the tool edge, after elimination of the centeringaction aiecting it, so as to bring the edge out of contact with thebored surface. If, however, the edge is not in highest position, itcannot be retracted from the bored 10 surface but is pressed thereon bythe weight of the boring bar which cannot be removed without injuringthe bored surface or the edge itself.

It has been proposed to overcome these drawbacks by providing the twoportions of the boring bar for mutual .centering with cooperatingannular guides and making use of avtension member which will rigidlyco-nnect both portions and if released permit the tool carrying portionto swing out. This construction is, however, open tothe objection thatprior to the withdrawal of the bar from the bore the tensio-n memberconnecting both portions has to be released to permit the bar to beswung back by the action of a spring.

The invention eliminates these defects of the knowntypes of boring barsand makes possible automatic and positive retraction of the tool edgefrom the bored surface at any position of the edge, by providing in acentral longitudinal bore of the bar a slide member subjected to the 3action of a spring to abut against the center point of the driver, whichmember by means of a cone or an inclined surface and the radialdisplacement of a thrust pin causes the tool to be lifted off from theworking surface at any position of the edge.

One form of the invention is illustrated by way of example only in theaccompanying drawing, in which a boring bar according to the inventionis shown, partly in longitudinal section.

In the drawing:-

Figure 1 shows an elevation partly in section of a boring bar andassociated parts embodying the invention;

Fig. 2 is a cross section taken on line II-II of Fig. l, on a largerscale; and

Fig. 3 is a cross section taken on line III-III of Fig. 1, also on alarger scale.

Referring to the drawing, I is a non-pivotal part of the boring bar and2 the pivotable part thereof which at its: ends is arranged between thecenters 3 and 4. The center 3 has a flattened conical end which extendsinto a bore 5 of the part 2 and engages a slide member 6, longitudinallydisplaceable in the bore 5 against the action of a compression spring 8.The center 3 also (Cl. 'T7-56) engages a conical seating I9 on the mouth'of the bore in the boring bar 2, to center said end during operation.

The slide member 6 has an inclined surface l cooperating in a mannerdescribed hereinafter 5 with a thrust pin I2 iixed in the pivotable part2 near its end. The part 2 is pivoted in the part I by means of auniversal joint comprising pivot pins I3, I5 and an elastic ring Ill,the part 2 being jointed to the ring I4 by the pivot pin I3, and 10 thering I ll jointed to the part I by the pivot pin I5. The pivot pin I5traverses a bore in the ring I4 which is large enough to permit limitedaxial movement of the part I relatively to the nonpivoting part l.

If after completion of the boring operation carried out'by the tools 9and I0 the boring bar l, 2 is withdrawn from the centering abutment II,the spring 8 will cause displacement of the slide member .Ii relativelyto the part 2 and the 2O thrust pin I2 will co-operate with the inclinedsurface 'I to lower the left hand end of the part 2. Consequently, thepart 2 will be swung about the shaft I3 of the joint M, I5 connectingthe driving part I with the pivotable part k2, 25 this movement beingpossible owing to the flattened point of the conical end sliding on theflat end of the member 6 in such a way that the. tools 9 and I0 will beretracted from the working surfaces and the boring bar I, 2 can be with-30 drawn from the bore without being damaged.

The elasticity of the ring also prevents transmission of vibration fromthe drive to the tool.

In the construction shown the attachment of the boring bar to thespindle of the drilling ma- 35 chine is: particularly simplied byproviding a sleeve IG carrying the center 3, with a Morse taper on itsouter face I'I. To obtain vibrationless driving of the spindle it isadvisable to arrange the center 3 within the bearing I8 of the drive.

The operation of the present invention is as follows:

The center point of the member 3 is somewhat flattened and merelyengages or abuts the end surface of the slide G in such a manner thatthis end can move transversely to the center 3. Upon withdrawing thecenter support II, the tool bar 2, under the action of the spring 8, andutilizing the axial plan of the universal joint I4, I5, is forced to theright carrying with it the thrust pin I2, while the slide 6 remains heldby the spring 8 against the flat point of the center 3. The conical seatI9 at left-hand end of the tool bar 2 thus separates from the center 3and the 55 movement; of the thrust pin I2, which is mounted with play inthe Wall of the bore 5 and of which the outer end bears against theinner surface of the bushing I6, causes the slide member and with it theleft-hand end ofthe tool bar to move upwardly.

From the foregoing, the importance of the universal joint I4, I5 isevident. This joint allows the tilting movement of the tool bar 2, bymeans of the pressure on the thrust pin I2 and the spring 8, to withdrawthe cutters from the work. The tool bar obviously can move only in oneVdirection which is imposed upon it by the movement of the thrust pin I2against the slide E. Another purpose of the universal joint isl totransmit the drive of the driving member I to the tool bar 2 withoutvibration and bending action.

Obviously the universal joint supports the tool bar after withdrawing ofthe support I I, and the tool bar tilts about the axis I3. The universaljoint therefore cannot be omittedV as otherwise the tool bar would notbe driven bythe driving member I, nor could it tilt about the pin I3.

I claim:-

1. A boring bar foroperation between two centers comprising a drivingmember, a tool carrying member having an axial bore at one end in whichone of the centers engages a slide member in said bore, said slidemember having an inclined side face and abutting at one end against aattened point of said center, a spring operative between the slidemember and the tool carrying member, joint means connecting the toolcarrying member with the driving member and enabling the tool carryingmember to pivot in the driving member in any direction trans' verse totheir common axis,A said joint means providing for limited axialmovement between said driving and tool carrying members, and a thrustpin in the wall of said bore and cooperating with the inclined surfaceof the slide member to pivot the tool carrying member about the joint asa result of said limited axial movement.

2. A boring bar for operation between two centers, comprising a drivingpart, a tool-carrying part, means jointedly connecting said partsincluding a pivot pin about which the tool-carrying part can swingtransversely to its axis, a slide member longitudinally displaceable inan axial bore in one end of the tool-carrying part and slidably abuttingat one end against one of the centers which extends into said bore, saidslide member having an inclined face, a compression spring o-peratingbetween the tool-carrying part and the other end of said slide member,said spring being coaxial with said tool-carrying part, and a thrust pincooperating with the inclined face of said slide member and adapted tobe radially moved by axial displacement of the said slide member by saidspring on retraction of the other center from the boring bar, the jointmeans being adapted to allow a limited axial movement of thetool-carrying part relatively to the driving part.

3. A boring bar for operation between two centers comprising a drivingmember, a tool carrying member having an axial bore at one end in whichone of the centers engages a, slide member in said bore, said slidemember having an inclined side face and abutting at one end against aattened point of said center, a spring i operative between the slidemember and the tool carrying member, joint means connecting the toolcarrying member with the driving member and enabling the tool carryingmember to pivot in therdriving member in any direction transverse toVtheir common axis, said joint means providing for limited axial movementbetween said driving and tool carrying members, and a thrust pin in thewall of said bore and cooperating with the inclined surface of the slidemember to pivot Y the tool carrying member about the joint as a resultof said limited axial movement, said joint means comprisingV a universaljoint having one of its parts of elastic material.

4. A boring bar for operation between two centers, comprising a drivingpart, a tool-carrying part, means jointedly connecting said partsincluding a pivot pin about which the tool-carrying part can swingtransversely to its axis, a slide member Ylongitudinally displaceable inan axial bore in one end of Vthe too-l-carrying part Vand slidablyabutting at one end against one of the centers which extends into saidbore, said slide memberV having an inclined face, a compression springoperating between the tool-carrying partv and the other end of saidslide member, said spring being coaxial with said tool-carrying part,and a thrust pin cooperating with the inclined face of said slide memberand adapted to be radially moved by axial displacement of the said slidemember by said spring on retraction of the other center from the boringbar, the joint means being adapted to allow a limited axial movement ofthe vtool-carrying part relatively to the driving part, and comprising auniversal joint having one ofV its parts of elastic material. Y

FRITZ WALTHER.

